It is known that there are emergency call boxes on most freeways. A user can access said Call Box to contact an emergency dispatch operator. Some of these call boxes have been provided with telecommunications devices for the deaf (TTD) or text telephony (TTY).
A separate enclosure is mounted below the main housing of the call box which contains a motorized key plate. Attached to the key plate is a TTD keypad, which is a membrane type keypad. This forms of what we will refer to as the keyboard. The keyboard is used in conjunction with the display module. The decision to use a standard handset or keyboard and display is made by the motorist. When the TTY is selected the keyboard extends automatically so the user can bi-directionally communicate with an emergency dispatch operator without the need for voice communication.